Well man i dont get shakes with clen anymore, maybe when i first ever started using it. The way i know now is the raise in bodytemp. I have tried various types of clen and to me the chinese generic is the strongest, but also loved axio and geneza worked well also. 2 wks on 2 wks off is probably the way to go if you dont have ketotifen on hand. I always have keto on hand so that i can run it for 2 weeks on and then only take about 5 days off with 1mg keto everynight during those 5 days. That works really well for me